1. Field of the Invention
The present invention relates to a vehicle and a control method of the vehicle. More specifically the invention pertains to a vehicle equipped with an internal combustion engine that outputs power and with a motor that is capable of outputting at least a regenerative braking force to an axle of the vehicle, as well as to a control method of such a vehicle.
2. Description of the Related Art
The known structure of a prior art braking device for the vehicle includes a booster that utilizes a negative pressure produced by an internal combustion engine to amplify the driver's pedal force of a brake pedal, a master cylinder that produces a fluid pressure according to the driver's pedal force amplified by the booster, an electric pump as a hydraulic pressure generation source, and wheel cylinders that use the master cylinder and the electric pump as the hydraulic pressure source to apply a braking force to corresponding wheels (see, for example, Japanese Patent Laid-Open Gazette No. 2004-224119). In the prior art braking device of this known structure, a motor for the electric pump is actuated when the negative pressure produced by the internal combustion engine is lowered to or below a preset level. The actuated electric pump is used as the hydraulic pressure source to increase the pressure of the wheel cylinders. This structure ensures stable generation of the braking force against the driver's pedal force even in the event of a variation in driving state of the internal combustion engine. In another known structure of a prior art braking device capable of regenerative cooperation control for a hybrid vehicle, a pressure regulator regulates the liquid pressure, which is generated by a liquid pressure generator including an accumulator and a power-driven pump, according to the driver's pressing force of a brake pedal and outputs the regulated liquid pressure. A master cylinder is actuated by a supply of the liquid pressure to an auxiliary liquid pressure chamber. Both the output liquid pressures of the master cylinder and the pressure regulator are supplied to wheel cylinders, so as to apply a braking force to the wheels of the vehicle (see, for example, Japanese Patent Laid-Open Gazette No. 2004-182035).